Light olefins, i.e., ethylene and propylene, are two important basic chemical materials with an increasing demand. Generally, ethylene and propylene are produced from petroleum. Due to limited supply and higher price of petroleum resources, the cost of producing ethylene and propylene from petroleum resource is continuously increasing. Recently, techniques for preparing ethylene and propylene by conversion converting of petroleum alternatives have been developed. Oxygen-containing compounds, such as alcohols (for example, methanol and, ethanol), ethers (for example, dimethyl ether and, methyl ethyl ether), and esters (for example, dimethyl carbonate and, methyl formate) and the like, which can be converted from petroleum alternatives, such as coal, natural gas, and biomass and the like. Some oxygen-containing compounds, such as methanol, can be produced from coal or natural gas on a large scale, reaching to production scales of, for example, in millions of tons. Due to the abundant supply of such oxygen-containing compounds, in combination with the more economically efficient technique of olefin production by conversion converting from petroleum alternatives, the Oxygenate To Olefins processes (OTO), such as the Methanol to Olefins processes (MTO), have drawn more and more attention. Examples of such processes are disclosed in U.S. Pat. Nos. 4,499,327 and 6,166,282, and Chinese Patent No. CN1723262.
The reaction-regeneration system for preparing light olefins from methanol is fundamentally different from the traditional reaction-regeneration system for catalytic cracking. The difficulty for start-up of MTO process is also greater than that of catalytic cracking. Moreover, during the start-up process for the traditional reaction-regeneration system a burning oil is generally sprayed into the regenerator, which may cause damage to the catalysts. The present invention provides a new start-up method for a reaction-regeneration unit used to prepare light olefins from methanol, which provides a solution to the above problem.